Vision in the brain
9.12.25
(cont'd)
Agenda
- Slido - project groups
- Exit Ticket Recap
- Receptive Fields
- Retina, LGN, and V1
- Extrastriate (visual) cortex
- What & where pathways
today's slido
main route for visual info in the brain: retina -> LGn -> V1
1st stop
2nd stop
Lateral geniculate nucleus (LGN) - Part of the thalamus that receives signals from the axons of retinal ganglion cells
for visual info in the brain
for visual info in the brain
Primary visual cortex (V1) - part of occipital lobe receiving signals from LGN
Optic radiations - axons carrying signals from the LGN to V1
Optic nerve - Bundles of axons of retinal ganglion cells from each eye
the lateral geniculate nucleus (Lgn)
Multiple layers with 2 main types of cells - parvocellular, or P-type (specialized for detail & color in fovea) - magnocellular, or M- type (specialized for motion in periphery)
receptive fields in the retina
RETINOTOPIC MAPPING:
signals from retinal ganglion cells with receptive fields next to each other on the retina travel to neurons that are next to each other in each visual area of the brain
->
->
Retinal ganglion cells (RGC) aligned at an angle of 50°
each connect with LGN cells with similar receptive field locations.
all connect with one simple cell in V1
overlapping receptor fields in lgn
Overlap of receptive fields in LGN -> perception of continuous lines in V1
receptive fields in the retina
receptive field - region of a sensory surface (i.e. the retina) that, when stimulated, changes the firing rate of the corresponding neuron (i.e. retinal ganglion cell)
receptive fields in the LGN
receptive fields in the V1
V1 simple cells respond selectively to their favorite line orientation
Each cortical column in V1 corresponds to a distinct part of the retinal image
functional modules in extrastriate cortex
Area MT (V5) contains neurons that respond strongly and selectively to motion in receptive field
On this graph using polar coordinates, the radius of the tuning function at any direction indicates the magnitude of the neuron’s response.
2 main processing streams originate in primary visual cortex (v1):
Where
Ventral stream: identifying objects (what)Damage causes problems in perceiving faces and objects. Dorsal stream: assessing the location of objects (where), and guiding our movement toward themDamage causes optic ataxia: difficulty using vision to reach for and grasp objects
What
ventral & Dorsal streams the "What" & "where" pathways
Remember to complete your Exit Ticket
Exit Ticket
Next class: Visual Object Recognition
8 - Vision in the brain (cont'd; 9.12.25)
Morgan Paladino
Created on September 12, 2025
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Transcript
Vision in the brain
9.12.25
(cont'd)
Agenda
today's slido
main route for visual info in the brain: retina -> LGn -> V1
1st stop
2nd stop
Lateral geniculate nucleus (LGN) - Part of the thalamus that receives signals from the axons of retinal ganglion cells
for visual info in the brain
for visual info in the brain
Primary visual cortex (V1) - part of occipital lobe receiving signals from LGN
Optic radiations - axons carrying signals from the LGN to V1
Optic nerve - Bundles of axons of retinal ganglion cells from each eye
the lateral geniculate nucleus (Lgn)
Multiple layers with 2 main types of cells - parvocellular, or P-type (specialized for detail & color in fovea) - magnocellular, or M- type (specialized for motion in periphery)
receptive fields in the retina
RETINOTOPIC MAPPING:
signals from retinal ganglion cells with receptive fields next to each other on the retina travel to neurons that are next to each other in each visual area of the brain
->
->
Retinal ganglion cells (RGC) aligned at an angle of 50°
each connect with LGN cells with similar receptive field locations.
all connect with one simple cell in V1
overlapping receptor fields in lgn
Overlap of receptive fields in LGN -> perception of continuous lines in V1
receptive fields in the retina
receptive field - region of a sensory surface (i.e. the retina) that, when stimulated, changes the firing rate of the corresponding neuron (i.e. retinal ganglion cell)
receptive fields in the LGN
receptive fields in the V1
V1 simple cells respond selectively to their favorite line orientation
Each cortical column in V1 corresponds to a distinct part of the retinal image
functional modules in extrastriate cortex
Area MT (V5) contains neurons that respond strongly and selectively to motion in receptive field
On this graph using polar coordinates, the radius of the tuning function at any direction indicates the magnitude of the neuron’s response.
2 main processing streams originate in primary visual cortex (v1):
Where
Ventral stream: identifying objects (what)Damage causes problems in perceiving faces and objects. Dorsal stream: assessing the location of objects (where), and guiding our movement toward themDamage causes optic ataxia: difficulty using vision to reach for and grasp objects
What
ventral & Dorsal streams the "What" & "where" pathways
Remember to complete your Exit Ticket
Exit Ticket
Next class: Visual Object Recognition